Here's the car in question. Not exactly stock, with the mods pertinent here being more roll stiffness than OE and tires mounted on wheels half an inch wider than the max-recommended width for the size.

As it happened, I was also headed for an autocross, just not the one pictured here. Think early Sunday morning, with the sun just about to rise.

I hit a piece of metel with the left rear tire travelling on the up-side of a rather long bridge. About an inch long sidewall slice, though the metal stayed embedded (might still have it somewhere). Anyway, I heard the pop like a stone would make and figured that I'd just pay attention but drive normally otherwise. Over the bridge, no real difference in handling feel, so I hit the two ramps to the highway with average-ish enthusiasm.

Funny you mentioned 70 mph curves as being a place where you wouldn't want to lose a bead, as that's about what I was running through the second ramp. It did feel like I'd lost a little rear cornering stiffness, like the tire had lost a little pressure, but only a little.

So I backed it off, ran another mile or so (elevated roadway, no pulloff areas or "breakdown lane" to speak of). Did an easy lane change maneuver by autocross standards, and it finally felt squishy out back handling-wise and the left rear had dropped slightly. At that point, it was time to pull over regardless. Else I'd be in it for a hard-to-find wheel as well (the wheel was completely undamaged and I still have it).

I had travelled a couple of miles from the point where the puncture occurred, taking maybe a little over two minutes.

The tire was fully 80% of the way to this condition when I changed it (and for the lane change maneuver as well). I tend to keep souvenirs of various failures, and I just took the picture a few minutes ago.

Did I mention that both of the ramps were righthanders (which transfers load to the left side tires)?

I'm in no way suggesting that people go out and try to duplicate this episode. Only that some fairly severe occurrences can be dealt with by the driver without any electronic help if he's on his game and paying attention.

No doubt the mods mentioned helped. The somewhat higher lateral stiffness from being stretched slightly meant that the right rear was covering for the LR by more than it would with a more "normal" wheel and tire package.

TPMS wouldn't have provided any warning within that time span, or at the very very least could not have been counted on to do so. And the car remained eminently controllable at the prevailing speed of other traffic, all the way down to zero pressure in that tire.

Norm

Last edited by Norm Peterson; 01-18-2013 at 12:40 PM..

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